**4. Conservation implications and future research**

100 New Approaches to the Study of Marine Mammals

**105**

**195**

**138/163/164**

*r* **=0.27** *p* **= 0.041**

**137**

**158/160**

**180**

**0.0**

IUPAC system.

**0.5**

**1.0**

**1.5**

**Log H (Pa m3/mol)**

**2.0**

**2.5**

**118**

**170/190**

and common pathway of POPs of atmospheric origin.

**3.6. Health risk assessment** 

**194**

**43/49**

**123**

**<sup>60</sup> <sup>61</sup>**

**110**

**187**

**74**

**86/97**

**52**

**136**

**101**

**95**

**66**

**149**

**87 92**

**47/48/75**

**85**

**<sup>141</sup> <sup>142</sup> <sup>144</sup> <sup>146</sup>**

**156**

**99**

**<sup>151</sup> <sup>153</sup> <sup>154</sup>**

**<sup>171</sup> 172/192 <sup>174</sup> <sup>177</sup> <sup>178</sup> <sup>175</sup> <sup>179</sup>**

**191 193**

**167**

**-1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 0.40 0.60 0.80 1.00**

**PC 1 (40.1%)**

**Figure 7.** Relationship between the Henry's law constant (Log H) for polychlorinated biphenyl (PCB) congeners and the first principal component (PC1). PC1 is significantly correlated with Log H for PCB congeners, suggesting that Galapagos sea lions from the remote Galapagos Islands are more exposed to light PCB mixtures, consistent with atmospheric signals. Numbers are PCB congeners based on the

The long range atmospheric transport coupled with global fractionation have usually been described as the major mechanism delivering POPs from lower or mid latitudes to the polar regions [11, 63, 64], but it is likely that a similar mechanism or redistribution from mid latitudes may be also expanding or delivering volatile or semi-volatile pesticides such as HCHs and DDTs to isolated islands around the equator (i.e., the Galapagos Archipelago). These observations suggest that the contamination by organochlorine pesticides might be coming from both local and continental sources because pesticides were used in the recent past in countries in the southern hemisphere [49, 65]. Trans-Pacific air pollution of contaminants from tropical Asia to the eastern Pacific [63, 66] cannot be ruled out as a global

The health risk of POP biomagnification in Galapagos sea lions is of serious concern in the long term, as we have previously reported that 1% of the male pups exceeded the *p*,*p*'-DDE toxic effect concentration associated with potent anti-androgenic effects [35]. DDT concentrations in Galapagos sea lion pups are near levels expected to be associated with impacts on the immune systems, and in minor degree on the endocrine systems in males. Adult male Galapagos sea lions can be expected to exhibit DDT concentrations that are

**<sup>128</sup> <sup>130</sup> <sup>132</sup> <sup>135</sup>**

**183 185**

**196/203 <sup>197</sup> <sup>201</sup> <sup>202</sup> <sup>200</sup>**

**155**

The Galapagos is one of the last evolutionary biology labs to preserve biodiversity. Yet, it has already been declared a UNESCO-Heritage site at risk because of invasive species, escalating human population growth and burgeoning tourism [68]. This study corroborated that POPs biomagnify to a significant degree in the tropical marine food chain of the Galapagos' marine ecosystem. This has important implications for management and control of organochlorine pesticides and conservation of marine ecosystems in tropical regions since pollution in the Galapagos has been categorized as an aesthetic issue rather than a chronic problem.

Recently, the World Health Organization (WHO) has reactivated the use of the malaria mosquito-fighting pesticide DDT in tropical countries because of increasing malaria cases [69]. While the concentrations of DDT and associated health risks in wildlife are generally believed to be declining, this may no longer be the case in tropical countries where DDT is increasingly used and can biomagnify in food chains. A renewed use of DDT to combat malaria is likely to increase DDT concentrations in the Southern Hemisphere and in particular put bird and marine mammal populations at greater risk because of the biomagnification of these substances in their food webs.

Since the ratification of the UN Stockholm Convention on POPs by Ecuador in 2004, the National Plan for the Inventory and Management of POPs was undertaken [70, 71]. DDT is included on Schedule 2 of the Stockholm Convention because of its damaging health effects in human and wildlife populations. Continuation of this initiative will help to control DDT contamination in the Galapagos. While DDT can save human lives, it can also adversely affect wildlife, local food production and opportunities for ecotourism. DDT use requires that tradeoffs need to be made between the conservation of valued, sensitive wildlife (e.g. Galapagos sea lions), fragile ecosystems and public health programs to control malaria.

Additional research and field sampling efforts may include other organisms integrating the trophic guilds of the Galapagos sea lion food web by measuring legacy and emerging POPs, stable isotopes and subsequent estimations of trophic levels. This will allow assessing in a higher degree the food web amplification of pollutants through the use of TMFs and food web bioaccumulation models in marine ecosystem of the remote Galapagos Islands.

Our findings provide sound scientific information on food chain contamination and potential ecological impacts in the Galapagos that can be used for conservation plans at the ecosystem level, and portrays the implications for environmental management and control of bioaccumulative, persistent and toxic contaminants (e. g. DDT). Finally, this study serves as a reference point against which possible future impact of DDT use in tropical marine ecosystems can be measured, underlying the use of more environmental friendly substances to control pests and vectors in developing countries.

Assessing Biomagnification and Trophic Transport of Persistent Organic Pollutants in the Food Chain of the Galapagos Sea Lion (*Zalophus wollebaeki*): Conservation and Management Implications 103

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